Method and apparatus of hydrolytic saccharification of cellulosic biomass

ABSTRACT

The hydrolytic saccharification method and hydrolytic saccharification apparatus according to the present invention use a hydraulic cylinder-type pressurized reactor as a reactor for causing cellulosic biomass to be in a supercritical or subcritical state, and use a hydraulic cylinder-type steam compressor as a source of superheated steam, such that the reactor and the compressor are operated in conjunction with each other. Surplus hydraulic pressure that is generated when hydrolysis of the cellulosic biomass is completed is recovered as compression power of the hydraulic cylinder-type steam compressor. Moreover, flash steam generated from slurry containing a hydrolysate is supplied to the hydraulic cylinder-type steam compressor for cyclic use of the flash steam.

TECHNICAL FIELD

The present invention relates to a method and apparatus for use in producing saccharides by hydrolyzing cellulosic biomass in a supercritical or subcritical state.

BACKGROUND ART

As part of biomass energy utilization, attempts have been made to obtain ethanol (bioethanol) by hydrolyzing cellulose or hemicellulose, which are major components of plants. Ethanol thus obtained is planned to be utilized mainly as a fuel to be mixed into an automobile fuel or as an alternative fuel for gasoline.

Major components of plants include cellulose (a polymer of glucose which is a C6 monosaccharide composed of six carbon atoms), hemicellulose (a polymer of C5 and C6 monosaccharides; a C5 monosaccharide is composed of five carbon atoms), lignin, and starch. Ethanol is produced by using saccharides as raw materials, such as a C5 monosaccharide, a C6 monosaccharide, and an oligosaccharide which is a complex of these saccharides. Ethanol is produced through fermentation of microorganisms such as yeast.

For hydrolyzing cellulosic biomass containing cellulose or hemicellulose into saccharides, there are the following three possible methods to be industrially applied: 1) a method of hydrolyzing such biomass by utilizing oxidizing power of a strong acid such as sulfuric acid; 2) a method of hydrolyzing such biomass by utilizing an enzyme; and 3) a method utilizing oxidizing power of supercritical or subcritical water. However, the acidolysis method 1) indispensably requires a treatment for neutralizing the added acid after hydrolysis of cellulose or hemicellulose into saccharides and before fermentation of the saccharides into ethanol because the added acid acts as an inhibitor against the fermentation by yeast. The cost of such treatment makes it difficult to put this method into practical use from an economic standpoint. Although the enzymolysis method 2) can be realized by a process under a normal temperature and constant pressure, no effective enzyme for the method has been found yet, and even if an effective enzyme is found, the outlook for industrial-scale realization of the method is still unclear in terms of cost efficiency, because such an enzyme is expected to incur a high production cost thereof.

As the method 3) of hydrolyzing cellulosic biomass into saccharides by using supercritical or subcritical water, there are disclosed methods as described below. Patent Literature 1 discloses a method of producing water-insoluble polysaccharides, which is characterized by hydrolysis of cellulose powder that is performed by bringing the powder into contact with pressurized hot water of 240 to 340° C. Patent Literature 2 discloses a method including: hydrolyzing biomass chips for a predetermined time period with hot water pressurized to a saturated vapor pressure or higher at 140 to 230° C., thereby extracting hemicellulose; and then hydrolyzing the biomass chips with pressurized hot water heated to a temperature not lower than a cellulose hydrolyzing temperature, thereby extracting cellulose. Patent Literature 3 discloses a method of producing glucose and/or water-soluble cello-oligosaccharides, which is characterized in that cellulose having a mean polymerization degree of not less than 100 is hydrolyzed by: bringing the cellulose into contact reaction with supercritical or subcritical water at a temperature of not lower than 250° C. and not higher than 450° C. and at a pressure of not lower than 15 MPa and not higher than 450 MPa for a time period of not less than 0.01 second and not more than 5 seconds; then cooling down the cellulose; and thereafter bringing the cellulose into contact with subcritical water at a temperature of not lower than 250° C. and not higher than 350° C. and at a pressure of not lower than 15 MPa and not higher than 450 MPa for a time period of not less than 1 second and not more than 10 minutes.

In the case of performing hydrolysis or oxidative decomposition of organic matter such as biomass by using supercritical or subcritical water, high-pressure water in which the organic matter is dispersed is heated up quickly and a supercritical or subcritical state is maintained for a certain period of time, and thereby a hydrolysis reaction is caused. After the reaction is completed, it is necessary to quickly cool down the reaction system to stop further chemical reactions from occurring. As one example of a reaction apparatus capable of such quick heating and quick cooling, Patent Literature 4 discloses a reactor which is configured to pressurize steam from a boiler by using a piston, thereby producing supercritical or subcritical water. Patent Literature 4 also discloses: driving the cylinder of the reactor by means of a crank mechanism or cam mechanism; recovering steam from a product removed from the reactor; and utilizing the pressure of the steam for driving the crank mechanism or cam mechanism.

Patent Literature 5 discloses an organic matter system for supplying an organic matter-containing fluid at a stable flow rate while keeping the fluid in a high-temperature and high-pressure state. The system disclosed in Patent Literature 5 includes: a first driver configured to receive a processed high-pressure fluid and its pressure by the piston of a cylinder and transmit the pressure as force to pressurize an unprocessed fluid; and a second driver configured to supplement the first driver with driving force. The system is configured to reduce the energy of the processed high-pressure fluid by using a back pressure valve, and then introduce the fluid into the cylinder of the first driver.

CITATION LIST Patent Literature

PTL 1: Japanese Laid-Open Patent Application Publication No. 2000-186102

PTL 2: Japanese Laid-Open Patent Application Publication No. 2002-59118

PTL 3: Japanese Laid-Open Patent Application Publication No. 2003-212888

PTL 4: Japanese Laid-Open Patent Application Publication No. 2002-263465

PTL 5: Japanese Laid-Open Patent Application Publication No. 2000-233127

SUMMARY OF INVENTION Technical Problem

In the apparatus disclosed in Patent Literature 4 in which the crank mechanism or cam mechanism is driven by the recovered steam, it is unavoidable to synchronize the timing of recovering the steam with the timing of compressing the reactor with the cylinder. With the apparatus disclosed in Patent Literature 4, effective utilization of the latent heat of the steam cannot be realized. Further, in a case where the rotational frequency of the crank mechanism or cam mechanism is set to be constant, it is difficult to maintain the cylinder of the reactor in a pushed state for a certain period of time, and difficult to arbitrarily change the speed of pushing or pulling the cylinder while in operation. Thus, there is not much freedom in changing operating conditions.

Also in the system disclosed in Patent Literature 5, it is unavoidable to synchronize the driving of a primary cylinder with the driving of a secondary cylinder since the piston of the primary cylinder and the piston of the secondary cylinder are connected by a single piston rod.

An object of the present invention is, in a method and apparatus of hydrolyzing cellulosic biomass in a supercritical or subcritical state, to reduce compression power by recovering surplus pressure at the time of reducing the pressure in a reactor, and to obtain freedom in the timing of operating the reactor and the timing of operating a compression mechanism. Another object of the present invention is to recover latent heat through cyclic use of flash steam, thereby improving thermal efficiency.

Solution to Problem

The inventors of the present invention conducted diligent studies to solve the above problems. As a result of the diligent studies, the inventors arrived at using a hydraulic cylinder-type pressurized reactor as a reactor for causing cellulosic biomass to be in a supercritical or subcritical state, and using a hydraulic cylinder-type steam compressor as a source of superheated steam, and then attempted to operate the reactor and steam compressor in conjunction with each other. Then, the inventors have found that the above-described problems can be solved by performing the following: recover surplus hydraulic pressure when hydrolysis of the cellulosic biomass is completed to use the recovered pressure as compression power of the hydraulic cylinder-type steam compressor; and supply flash steam generated from slurry containing a hydrolysate to the hydraulic cylinder-type steam compressor for cyclic use of the flash steam. As a result, the inventors have accomplished the present invention.

Specifically, the present invention relates to a method of hydrolytic saccharification of cellulosic biomass, in which cellulosic biomass is hydrolytically saccharified by pressurizing slurry of the cellulosic biomass together with superheated steam into a supercritical or subcritical state in at least one hydraulic cylinder-type pressurized reactor. The method includes: supplying, by at least one hydraulic cylinder-type steam compressor, the superheated steam to the hydraulic cylinder-type pressurized reactor; recovering hydraulic pressure of a hydraulic pressure chamber of the hydraulic cylinder-type pressurized reactor into a hydraulic pressure chamber of the hydraulic cylinder-type steam compressor at a time of reducing pressure in the hydraulic cylinder-type pressurized reactor to a pressure of the supercritical or subcritical state or lower after the cellulosic biomass has been hydrolytically saccharified, wherein a hydraulic pressure return passage of the hydraulic cylinder-type pressurized reactor and the hydraulic pressure chamber of the hydraulic cylinder-type steam compressor are in a state of connection via a hydraulic pressure recovery passage; and after supplying the slurry, the cellulosic biomass of which has been hydrolytically saccharified, into a flash tank, flash-evaporating the slurry and recovering flash steam into the hydraulic cylinder-type steam compressor.

The present invention also relates to an apparatus for hydrolytic saccharification of cellulosic biomass including: at least one hydraulic cylinder-type pressurized reactor configured to pressurize slurry of cellulosic biomass together with superheated steam into a supercritical or subcritical state; at least one hydraulic cylinder-type steam compressor configured to supply the superheated steam to the hydraulic cylinder-type pressurized reactor; and a flash tank configured to be supplied with the slurry that is removed from the hydraulic cylinder-type pressurized reactor, the slurry being in a high-temperature and high-pressure state, and to flash-evaporate the slurry. A hydraulic pressure return passage of the hydraulic cylinder-type pressurized reactor and a hydraulic pressure chamber of the hydraulic cylinder-type steam compressor are connected via a hydraulic pressure recovery passage. Hydraulic pressure of a hydraulic pressure chamber of the hydraulic cylinder-type pressurized reactor is recovered into the hydraulic pressure chamber of the hydraulic cylinder-type steam compressor through the hydraulic pressure recovery passage. The flash tank is connected to the hydraulic cylinder-type steam compressor. Flash steam generated from the slurry in the high-temperature and high-pressure state is recovered into the hydraulic cylinder-type steam compressor.

Preferably, the at least one hydraulic cylinder-type pressurized reactor comprises a plurality of hydraulic cylinder-type pressurized reactors, and the at least one hydraulic cylinder-type steam compressor comprises a plurality of hydraulic cylinder-type steam compressors. Preferably, the number of hydraulic cylinder-type steam compressors, which perform the supplying of the superheated steam to the hydraulic cylinder-type pressurized reactors, is the same as the number of hydraulic cylinder-type pressurized reactors. Preferably, the method includes cyclically recovering the hydraulic pressure of the hydraulic pressure chamber of each hydraulic cylinder-type pressurized reactor into the hydraulic pressure chamber of a corresponding one of the hydraulic cylinder-type steam compressors at the time of reducing the pressure in the hydraulic cylinder-type pressurized reactor to the pressure of the supercritical or subcritical state or lower after the cellulosic biomass has been hydrolytically saccharified, wherein the hydraulic pressure return passage of each hydraulic cylinder-type pressurized reactor and the hydraulic pressure chamber of the corresponding hydraulic cylinder-type steam compressor are in the state of connection via the hydraulic pressure recovery passage.

Preferably, the hydraulic pressure recovery passage is formed as a single passage at a portion connecting to the hydraulic pressure return passage and at a portion connecting to the hydraulic pressure chamber of the hydraulic cylinder-type steam compressor, and a remaining portion of the hydraulic pressure recovery passage is divided into a plurality of sub-passages. Preferably, each sub-passage is provided with a corresponding one of air chambers which are assigned different pressure storage setting values, respectively. Preferably, the method includes: storing the hydraulic pressure of the hydraulic pressure chamber of the hydraulic cylinder-type pressurized reactor sequentially in the air chambers in descending order of the pressure storage setting value; and then releasing the hydraulic pressure sequentially from the air chambers in ascending order of the pressure storage setting value to supply the hydraulic pressure to the hydraulic pressure chamber of the hydraulic cylinder-type steam compressor.

Preferably, a steam generator is connected to the flash tank, and the method includes: mixing steam supplied from the steam generator and the flash steam; and supplying resultant steam to the hydraulic cylinder-type steam compressor.

Preferably, an air and/or nitrogen supply device is connected to at least one of the flash tank and steam piping connecting the flash tank and the hydraulic cylinder-type steam compressor. Preferably, the method includes mixing air and/or nitrogen into steam to be supplied to a steam compression chamber of the hydraulic cylinder-type steam compressor, such that the air and/or nitrogen mixed into the steam is in an amount that is not less than 1/7 and not more than ⅓ of an amount of the steam.

The above object, other objects, features, and advantages of the present invention will be made clear by the following detailed description of preferred embodiments with reference to the accompanying drawings.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, compression power can be reduced by recovering surplus pressure (surplus hydraulic pressure) of a reactor into a steam compressor through a hydraulic passage. Since the present invention makes it possible to recover the latent heat of flash steam, high thermal efficiency is realized. Moreover, according to the present invention, the reactor and the steam compressor can be readily operated in conjunction with each other. Furthermore, condensation of steam within the steam compressor can be prevented by mixing air and/or nitrogen into the flash steam.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram illustrating an example of a processing apparatus for performing a method of hydrolytic saccharification of cellulosic biomass according to the present invention.

FIGS. 2A to 2D show conceptual diagrams illustrating the operations of a hydraulic cylinder-type steam compressor 5 a and a hydraulic cylinder-type pressurized reactor 1 a.

FIG. 3 is a schematic configuration diagram showing the vicinity of the hydraulic cylinder-type steam compressor 5 a and the hydraulic cylinder-type pressurized reactor 1 a of another example of the processing apparatus for performing the method of hydrolytic saccharification of cellulosic biomass according to the present invention.

FIG. 4 is a schematic configuration diagram showing an example of a conventional processing apparatus for performing a method of hydrolytic saccharification of cellulosic biomass.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention are described with reference to the drawings.

Embodiment 1

FIG. 1 is a schematic configuration diagram showing an example of a processing apparatus for performing a method of hydrolytic saccharification of cellulosic biomass according to the present invention. In FIG. 1, four hydraulic cylinder-type pressurized reactors and four hydraulic cylinder-type steam compressors are installed. However, the number of installed reactors and the number of installed steam compressors are not limited to four.

Slurry of cellulosic biomass is preheated as necessary, and then supplied to high-pressure steam supply passages 10 a to 10 d through slurry supply passages 11 and 11 a to 11 d. For example, the cellulosic biomass slurry may be obtained in the following manner: (1) vegetation biomass such as bagasse, sugar beet residue, or straw is ground to a grain size of several millimeters or less and then mixed with water to obtain slurry, the solid concentration of which is approximately 20 to 50 wt %; or (2) hemicellulose in cellulosic biomass is hydrolytically saccharified and then the residue is dehydrated, and thereafter, the residue (i.e., dehydrated cake) is mixed with water to obtain slurry, the solid concentration of which is approximately 20 to 50 wt %.

Meanwhile, steam supplied from a steam generator (not shown) such as a boiler is supplied to a flash tank 13 through a passage 12. The steam is also supplied to steam compression chambers 8 a to 8 d of hydraulic cylinder-type steam compressors 5 a to 5 d through recovered steam supply passages 14 and 14 a to 14 d. The temperature and pressure of the steam supplied from the steam generator are preferably in the ranges of 150 to 200° C. and 0.5 to 1.6 MPa, respectively.

If the temperatures in the recovered steam supply passages 14 and 14 a to 14 d and the steam compression chambers 8 a to 8 d are low, for example, at the start of the operation of the processing apparatus, then the temperature of the steam supplied from the recovered steam supply passage 14 tends to decrease. In such a case, there is a risk that the steam is condensed within the steam compression chambers 8 a to 8 d, resulting in that the latent heat of the steam is lost. It is considered that heat-insulating the steam piping is effective for preventing the condensation of steam during continuous operation of the processing apparatus. However, such heat insulation treatment results in a difficulty in heating up the steam piping at the start of the operation.

In this respect, the processing apparatus shown in FIG. 1 optionally includes piping 28, 28 a, and 28 b. The piping 28 is connected to an air and/or nitrogen supply device (not shown). Examples of the supply devices include an air compressor, a gas canister, and a nitrogen generator. As shown in FIG. 1, the piping 28 is divided into piping 28 a and piping 28 b. The piping 28 a is connected to the flash tank 13, and the piping 28 b is connected to the steam supply passages. Either the piping 28 a or the piping 28 b may be eliminated.

When air and/or nitrogen are supplied from the piping 28 a and the piping 28 b, the air and/or nitrogen are mixed into the steam in the flash tank 13 and the recovered steam supply passage 14. In this manner, air and/or nitrogen can be mixed into the steam to be supplied to the steam compression chambers 8 a to 8 d of the hydraulic cylinder-type steam compressors. As a result, the steam becomes an unsaturated state. Accordingly, the steam is less likely to be condensed when fed into the steam compression chambers 8 a to 8 d.

The air and/or nitrogen that are mixed into the steam to be supplied to the steam compression chambers are preferably in an amount that is not less than 1/7 and not more than ⅓ of the amount of the steam. Such a mixing ratio can be realized, for example, by the following manner: adjust the pressure of the air and/or nitrogen supplied to the flash tank 13 and/or the recovered steam supply passage 14 to be the same as the pressure of the steam; and adjust the flow rate of the air and/or nitrogen to obtain a predetermined ratio. The processing apparatus shown in FIG. 1 exerts advantageous effects that the steam is less likely to be condensed in the steam compression chambers 8 a to 8 d and the latent heat energy of the steam can be maintained easily even without heat-insulating the steam piping.

In a case where air and/or nitrogen are supplied from the piping 28 to the processing apparatus, it is preferred that the pressure in reaction chambers 4 a to 4 d is set to be approximately 10% to 30% higher than in a case where air and/or nitrogen are not supplied from the piping 28 to the processing apparatus. This is for setting the partial water vapor pressure to be the same as in a case where air and/or nitrogen are not supplied from the piping 28 to the processing apparatus.

<1. Recovery of Hydraulic Pressure>

All of the hydraulic cylinder-type steam compressors 5 a to 5 d operate in the same manner, and also, all of hydraulic cylinder-type pressurized reactors 1 a to 1 d operate in the same manner. Therefore, hereinafter, recovery of hydraulic pressure by a combination of the hydraulic cylinder-type steam compressor 5 a and the hydraulic cylinder-type pressurized reactor 1 a, according to the method of hydrolyzing cellulosic biomass of the present invention, is described based on FIGS. 2A to 2D.

(Description of FIG. 2A)

Steam is supplied to the steam compression chamber 8 a of the hydraulic cylinder-type steam compressor 5 a through the steam supply passage 14 a. Accordingly, the volume of a hydraulic pressure chamber 6 a becomes minimum, and hydraulic pressure in the hydraulic pressure chamber 6 a is returned to an oil tank 26 through hydraulic pressure return passages 19 a and 19. At the time, the hydraulic cylinder-type pressurized reactor la compresses the reaction chamber 4 a to which cellulosic biomass slurry and superheated steam have been supplied, thereby creating a supercritical or subcritical state and hydrolyzing the cellulosic biomass in such a state. Since the steam is compressed by the hydraulic cylinder-type steam compressor 5 a and then further compressed in the reaction chamber 4 a, the temperature and pressure of the steam are increased to the maximum. At the time of hydrolyzing the cellulosic biomass, it is preferred that the temperature and pressure in the reaction chamber 4 a are in the ranges of 350 to 400° C. and 18 to 30 MPa, respectively. The hydrolyzing time is preferably 0.1 to 30 seconds, and more preferably, 0.1 to 3 seconds.

A hydraulic passage 15 a is a high-pressure hydraulic passage in which the pressure is approximately 22 MPa. In the state shown in FIG. 2A, in order to compress the reaction chamber 4 a, to which the cellulosic biomass slurry and superheated steam have been supplied, to create a supercritical or subcritical state, a hydraulic cylinder 3 a is pushed by the hydraulic pressure of approximately 22 MPa.

(Description of FIG. 2B)

After the hydrolysis reaction of the cellulosic biomass is completed, the hydraulic cylinder-type pressurized reactor 1 a is quickly cooled down by reducing the pressure in the reaction chamber 4 a, and thereby further chemical reactions are stopped from occurring. At the time, hydraulic pressure in a hydraulic pressure chamber 2 a of the hydraulic cylinder-type pressurized reactor 1 a increases. Therefore, the hydraulic pressure in the hydraulic pressure chamber 2 a is recovered through a hydraulic pressure recovery passage 9 a into the hydraulic pressure chamber 6 a of the hydraulic cylinder-type steam compressor 5 a. As a result, steam in the steam compression chamber 8 a is compressed. Thus, power necessary for compressing the steam that is supplied to the steam compression chamber 8 a in the state shown in FIG. 2A can be reduced by utilization of the recovered hydraulic pressure.

(Description of FIG. 2C)

The steam in the steam compression chamber 8 a is further compressed, so that the steam becomes high-temperature and high-pressure (250 to 300° C., 3.9 to 8.5 MPa) superheated steam. At the time, the slurry from which saccharides have been produced, the temperature and pressure of which have been reduced to those of the subcritical state or lower, is discharged from the hydraulic cylinder-type pressurized reactor 1 a to a reacted slurry transport passage 20 a. Immediately before the discharging, the temperature and pressure of such reacted slurry are preferably in the ranges of 150 to 300° C. and 0.5 to 8.6 MPa, respectively. Meanwhile, cellulosic biomass slurry is loaded into a slurry feeding chamber 27 through the slurry supply passage 11 a.

A hydraulic passage 16 a is a low-pressure hydraulic passage in which the pressure is approximately 2 MPa. In the state shown in FIG. 2C, after the slurry from which saccharides have been produced is discharged from the hydraulic cylinder-type pressurized reactor 1 a to the reacted slurry transport passage 20 a, the hydraulic cylinder 3 a is pushed to the left end position in the diagram by the hydraulic pressure of appromixy 2 MPa, and thereby the volume in the reaction chamber 4 a is reduced to zero.

(Description of FIG. 2D)

The high-temperature and high-pressure superheated steam that is discharged from the steam compression chamber 8 a is supplied to the reaction chamber 4 a of the hydraulic cylinder-type pressurized reactor 1 a through a high-pressure steam supply passage 10 a. At the time, the cellulosic biomass slurry in the slurry feeding chamber 27 is concurrently supplied to the reaction chamber 4 a of the hydraulic cylinder-type pressurized reactor 1 a. Meanwhile, hydraulic pressure in the hydraulic pressure chamber 2 a of the hydraulic cylinder-type pressurized reactor 1 a is returned to the oil tank 26 through hydraulic pressure return passages 17 a and 17.

The state shown in FIG. 2D is followed by the above-descried state of FIG. 2A. Thereafter, the operations shown in FIG. 2A→FIG. 2B→FIG. 2C→FIG. 2D are repeated continuously. Since the recovery of hydraulic pressure is performed in such a continuous manner, the compression power can be reduced.

In the present invention, surplus pressure generated at the time of reducing the pressure in the reactor is recovered into the steam compressor as hydraulic pressure. Therefore, the reaction time in the reactor can be readily adjusted in accordance with the processing object and the amount of processing. For example, the reaction time can be adjusted for only a part of the cycle of the reactor. Thus, freedom in changing the operating conditions is significantly great. In this respect, the present invention is significantly different from the inventions disclosed in Patent Literatures 4 and 5.

<2. Recovery of Flash Steam>

Next, recovery of flash steam from reacted slurry is described. Reacted slurry that is discharged to the reacted slurry transport passage 20 a in the state shown in FIG. 2C is moved to the flash tank 13 through a reacted slurry transport passage 20. The reacted slurry is flash-evaporated in the flash tank 13, so that the pressure of the reacted slurry becomes approximately 0.1 to 1.6 MPa. Thereafter, the reacted slurry is moved from the bottom of the flash tank 13 to an external reservoir or external fermentation equipment by means of a pump 22.

Meanwhile, flash steam generated in the flash tank 13 is supplied to the hydraulic cylinder-type steam compressors 5 a to 5 d through the steam supply passages 14 and 14 a to 14 d. Then, the above-described processing steps are repeated. If the temperature and pressure in the flash tank 13 are lower than respective predetermined values, then steam is supplied to the flash tank 13 from the steam generator. On the other hand, if the temperature and pressure in the flash tank 13 are higher than the respective predetermined values, then surplus steam is discharged to the outside of the system.

According to the present invention, the reacted slurry can be quickly cooled down by flash evaporation, and flash steam generated from the reacted slurry is recovered as steam for use in hydrolyzing the cellulosic biomass. Thus, even the latent heat of the flash steam can be recovered. Since such steam recovery is performed continuously, thermal efficiency is improved.

Embodiment 2

FIG. 3 is a schematic configuration diagram showing a connection state between the hydraulic cylinder-type steam compressor 5 a and the hydraulic cylinder-type pressurized reactor 1 a in another example of the processing apparatus for performing the method of hydrolytic saccharification of cellulosic biomass according to the present invention. The processing apparatus shown in FIG. 3 is the same as the processing apparatus shown in FIG. 1 except that the hydraulic pressure recovery passage between the hydraulic cylinder-type steam compressor 5 a and the hydraulic cylinder-type pressurized reactor 1 a is different. In the processing apparatus shown in FIG. 3, a hydraulic pressure recovery passage 32 is connected to a hydraulic pressure return passage 17 a, and the hydraulic pressure recovery passage 32 is divided into four sub-passages 32 a to 32 d. The sub-passages 32 a to 32 d are provided with a set of respective hydraulic valves 33 a to 33 d.

The sub-passages 32 a to 32 d are connected to air chamber passages 35 a to 35 d, respectively. Air chambers P₁ to P₄ are provided at the end of the air chamber passages 35 a to 35 d, respectively. It is assumed here that pressures to be stored in the air chambers P₁ to P₄ are set to 3 MPa, 8 MPa, 13 MPa, and 18 MPa, respectively.

The air chamber passages 35 a to 35 d are connected to sub-passages 36 a to 36 d, respectively. The sub-passages 36 a to 36 d are provided with a set of respective hydraulic valves 37 a to 37 d. The sub-passages 36 a to 36 d are connected to the hydraulic pressure chamber 6 a of the hydraulic cylinder-type steam compressor 5 a via a hydraulic pressure supply passage 36.

Although FIG. 3 shows only the connection state between the hydraulic cylinder-type steam compressor 5 a and the hydraulic cylinder-type pressurized reactor 1 a, the same connection state is formed between the hydraulic cylinder-type steam compressors 5 b to 5 d and the hydraulic cylinder-type pressurized reactors 1 b to 1 d. That is, the sub-passages of the hydraulic pressure recovery passages connected to the respective hydraulic cylinder-type pressurized reactors 1 b to 1 d, and the sub-passages of the hydraulic pressure supply passages connected to the respective hydraulic cylinder-type steam compressors 5 b to 5 d, are connected to the air chamber passages 35 a to 35 d. The air chambers P₁ to P₄ are shared by the four hydraulic cylinder-type steam compressors and the four hydraulic cylinder-type pressurized reactors.

Next, a hydraulic pressure recovery operation performed by the processing apparatus shown in FIG. 3 is described. At the time of recovering the hydraulic pressure of the hydraulic pressure chamber 2 a into the hydraulic pressure chamber 6 a of the hydraulic cylinder-type steam compressor 5 a, first, a valve 34 of the hydraulic pressure return passage 17 a is closed and a valve 31 of the hydraulic pressure recovery passage 32 is opened. At the time, the sets of hydraulic valves 33 a to 33 d and 37 a to 37 d are in a closed state, and a valve 38 is also in a closed state. The hydraulic valve 33 d is opened. Accordingly, a hydraulic pressure of 18 MPa is sent through the sub-passage 32 d and the air chamber passage 35 d, and then stored in the air chamber P₄ for temporary storage. After the hydraulic pressure is stored, the hydraulic valve 33 d is closed.

Thereafter, the hydraulic valve 33 c is opened. Accordingly, a hydraulic pressure of 13 MPa is sent through the sub-passage 32 c and the air chamber passage 35 c, and then stored in the air chamber P₃ for temporary storage. After the hydraulic pressure is stored, the hydraulic valve 33 c is closed.

Subsequently, the hydraulic valve 33 b is opened. Accordingly, a hydraulic pressure of 8 MPa is sent through the sub-passage 32 b and the air chamber passage 35 b, and then stored in the air chamber P₂ for temporary storage. After the hydraulic pressure is stored, the hydraulic valve 33 b is closed.

Finally, the hydraulic valve 33 a is opened. Accordingly, a hydraulic pressure of 3 MPa is sent through the sub-passage 32 a and the air chamber passage 35 a, and then stored in the air chamber P₁ for temporary storage. After the hydraulic pressure is stored, the hydraulic valve 33 a is closed. Here, the valve 31 is also closed.

As a result of these operations, the hydraulic pressures of 3 MPa, 8 MPa, 13 MPa, and 18 MPa are temporarily stored in the air chambers P₁ to P₄, respectively. Hereinafter, a description is given of operations of supplying the hydraulic pressures temporarily stored in the respective air chambers P₁ to P₄ to the hydraulic pressure chamber 6 a of the hydraulic cylinder-type steam compressor 5 a.

First, the valve 38 is opened and then the hydraulic valve 37 a is opened. Accordingly, the hydraulic pressure of 3 MPa stored in the hydraulic pressure chamber P₁ is supplied to the hydraulic pressure chamber 6 a through the air chamber passage 35 a and the sub-passage 36 a. After the hydraulic pressure is supplied, the hydraulic valve 37 a is closed.

Thereafter, when the hydraulic valve 37 b is opened, the hydraulic pressure of 8 MPa stored in the hydraulic pressure chamber P₂ is supplied to the hydraulic pressure chamber 6 a through the air chamber passage 35 b and the sub-passage 36 b. After the hydraulic pressure is supplied, the hydraulic valve 37 b is closed.

Subsequently, when the hydraulic valve 37 c is opened, the hydraulic pressure of 13 MPa stored in the hydraulic pressure chamber P₃ is supplied to the hydraulic pressure chamber 6 a through the air chamber passage 35 c and the sub-passage 36 c. After the hydraulic pressure is supplied, the hydraulic valve 37 c is closed.

Finally, when the hydraulic valve 37 d is opened, the hydraulic pressure of 18 MPa stored in the hydraulic pressure chamber P₄ is supplied to the hydraulic pressure chamber 6 a through the air chamber passage 35 d and the sub-passage 36 d. After the hydraulic pressure is supplied, the hydraulic valve 37 d is closed. After the hydraulic pressure supply is completed, the valve 38 is also closed, and thus one cycle of the hydraulic pressure recovery is completed.

The sets of hydraulic valves 33 a to 33 d and 37 a to 37 d herein are configured as, for example, hydraulic counter balance valves and hydraulic sequence valves. Each valve has a function of automatically opening the corresponding passage when the pressure in the passage is within a preset pressure range, and a function of closing the passage when the pressure in the passage becomes out of the preset pressure range. The configurations of the sets of hydraulic valves 33 a to 33 d and 37 a to 37 d and the air chambers P₁ to P₄ shown in FIG. 3 are merely one example of hydraulic valve sets and air chambers usable in the embodiment of the present invention. Therefore, the configurations of hydraulic passages, hydraulic valve sets, and air chambers are not limited to the above.

In the state shown in FIG. 2B, the hydraulic pressure in the hydraulic pressure chamber 2 a of the hydraulic cylinder-type pressurized reactor 1 a is approximately 22 MPa, and the hydraulic pressure in the hydraulic pressure chamber 6 a of the hydraulic cylinder-type steam compressor 5 a is approximately 0.1 to 0.6 MPa. If, in such a state, the hydraulic pressure chamber 2 a and the hydraulic pressure chamber 6 a are directly connected, the flow velocity of the oil becomes too high due to the excessive hydraulic pressure difference. As a result, pressure loss and vibration are caused by frictional resistance of the hydraulic piping. The hydraulic pressure can be adjusted by installing a pressure reducing valve on the hydraulic piping. In this case, however, the pressure reducing valve acts as great resistance, and therefore, pressure loss is unavoidable.

Meanwhile, the present embodiment is characterized in that when the hydraulic pressure that is generated in the hydraulic pressure chamber 2 a of the hydraulic cylinder-type pressurized reactor 1 a is recovered into the hydraulic pressure chamber 6 a of the hydraulic cylinder-type steam compressor 5 a, hydraulic pressures are sequentially stored in the respective air chambers P₁ to P₄ in descending order of the pressure level, and then the hydraulic pressures are sequentially supplied from the respective air chambers P₁ to P₄ to the hydraulic pressure chamber 6 a in ascending order of the pressure level. In this manner, the hydraulic pressures are temporarily stored once in the respective air chambers, and then the stored hydraulic pressures are sequentially recovered in ascending order of the pressure level. Accordingly, even if the hydraulic pressure to be recovered is high, an excessive hydraulic pressure difference can be eliminated, and vibration of the piping can be prevented while preventing loss of the hydraulic pressure.

(Conventional Art)

FIG. 4 is a schematic configuration diagram showing an example of a conventional processing apparatus for performing a method of hydrolytic saccharification of cellulosic biomass. The method performed by the conventional processing apparatus is the same as the method of hydrolytic saccharification of cellulosic biomass according to the present invention in terms of that cellulosic biomass slurry and superheated steam are compressed by a hydraulic cylinder-type pressurized reactor into a supercritical or subcritical state and the cellulosic biomass is hydrolyzed in such a state. However, the conventional processing apparatus is not configured such that superheated steam supplied from a steam generator (not shown) such as a boiler is recompressed by a steam compressor and then supplied to the hydraulic cylinder-type pressurized reactor. Moreover, the conventional processing apparatus is not configured to recover flash steam from reacted slurry.

Hereinafter, the method of hydrolyzing cellulosic biomass that is performed by the processing apparatus shown in FIG. 4 is described. Cellulosic biomass slurry is supplied to a reaction chamber 46 of a hydraulic cylinder-type pressurized reactor 43 through a slurry supply passage 41. Meanwhile, superheated steam from a steam generator is supplied to the reaction chamber 46 of the hydraulic cylinder-type pressurized reactor 43 through a high-pressure steam supply passage 42. A hydraulic cylinder 45 of the hydraulic cylinder-type pressurized reactor 43 is operated by hydraulic pressure supplied from a hydraulic passage 47. Oil in a pressure oil tank 56 is supplied to the hydraulic passage 47 by means of a hydraulic pump 49.

The hydraulic cylinder-type pressurized reactor 43 compresses the reaction chamber 46, to which the cellulosic biomass slurry and high-pressure steam (i.e., superheated steam) have been supplied, to create a supercritical or subcritical state, and hydrolyzes the cellulosic biomass in such a state. After the hydrolysis reaction of the cellulosic biomass is completed, the pressure in the reaction chamber 46 is reduced and thereby the reaction chamber 46 is quickly cooled down, so that further chemical reactions are stopped from occurring. At the time, oil in a hydraulic pressure chamber 44 is returned through a hydraulic pressure return passage 48 to the oil tank 56 which is open to the atmosphere. Therefore, surplus pressure (surplus hydraulic pressure) cannot be recovered from the hydraulic cylinder-type pressurized reactor 43 as compression power for compressing the superheated steam.

The reacted slurry is supplied to a flash tank 51 through a reacted slurry transport passage 50. Flash steam generated in the flash tank 51 is discharged from the tank 51 through a flash steam exhaust passage 52, and then discharged by a heat exchanger 53 as condensation water. The discharged condensation water is reusable as a source of soft water used by the steam generator. In this case, however, the latent heat of the flash steam cannot be recovered. The reacted slurry is, after being cooled down, removed from the flash tank 51 to the outside through a saccharified solution passage 54 by means of a pump 55.

As described above, the method of hydrolyzing cellulosic biomass according to the present invention makes it possible to recover surplus pressure at the time of reducing the pressure in the reactor, thereby reducing compression power, and to recover latent heat through cyclic use of flash steam, thereby improving thermal efficiency. Moreover, in the method of hydrolyzing cellulosic biomass according to the present invention, surplus pressure generated at the time of reducing the pressure in the reactor is used, in the form of hydraulic pressure, as the compression power of the steam compressor. Thus, unlike the inventions disclosed in Patent Literatures 4 and 5, there is a lot of freedom in the operating timing of the reactor and the operating timing of the steam compressor. The method according to the present invention makes is possible to operate both the reactor and steam compressor in conjunction with each other in such a manner that the reactor and steam compressor are operated at their respective optimal timings.

From the foregoing description, numerous modifications and other embodiments of the present invention are obvious to one skilled in the art. Therefore, the foregoing description should be interpreted only as an example and is provided for the purpose of teaching the best mode for carrying out the present invention to one skilled in the art. The structural and/or functional details may be substantially altered without departing from the spirit of the present invention.

INDUSTRIAL APPLICABILITY

The method and apparatus of hydrolyzing cellulosic biomass according to the present invention are useful in the fields of bioenergy as a method and apparatus for use in hydrolyzing cellulosic biomass to produce saccharides.

Reference Signs List

1 a to 1 d: hydraulic cylinder-type pressurized reactor

2 a to 2 d: hydraulic pressure chamber

3 a to 3 d: hydraulic cylinder

4 a to 4 d: reaction chamber

5 a to 5 d: hydraulic cylinder-type steam compressor

6 a to 6 d: hydraulic pressure chamber

7 a to 7 d: hydraulic cylinder

8 a to 8 d: steam compression chamber

9 a to 9 d: hydraulic pressure recovery passage

10 a to 10 d: high-pressure steam supply passage

11, 11 a to 11 d: slurry supply passage

12: steam supply passage

13: flash tank

14, 14 a to 14 d: steam supply passage

15, 15 a to 15 d: hydraulic passage

16, 16 a to 16 d: hydraulic passage

17, 17 a to 17 d: hydraulic pressure return passage

18, 18 a to 18 d: hydraulic passage

19, 19 a to 19 d: hydraulic pressure return passage

20, 20 a to 20 d: reacted slurry transport passage

21: saccharified solution passage

22: pump

23, 24, 25: hydraulic pump

26: oil tank

27: slurry feeding chamber

28, 28 a, 28 b: piping

31, 34, 38: valve

32: hydraulic pressure recovery passage

32 a to 32 d: hydraulic pressure recovery passage (sub-passage)

33 a to 33 d: set of hydraulic valves

35 a to 35 d: air chamber passage

36: hydraulic pressure recovery passage

36 a to 36 d: hydraulic pressure supply passage (sub-passage)

37 a to 37 d: set of hydraulic valves

41: slurry supply passage

42: high-pressure steam supply passage

43: hydraulic cylinder-type pressurized reactor

44: hydraulic pressure chamber

45: hydraulic cylinder

46: reaction chamber

47: hydraulic passage

48: hydraulic pressure return passage

49: hydraulic pump

50: reacted slurry transport passage

51: flash tank

52: flash steam exhaust passage

53: heat exchanger

54: saccharified solution passage

55: pump

P₁ to P₄: air chamber 

1. A method of hydrolytic saccharification of cellulosic biomass, in which cellulosic biomass is hydrolytically saccharified by pressurizing slurry of the cellulosic biomass together with superheated steam into a supercritical or subcritical state in at least one hydraulic cylinder-type pressurized reactor, the method comprising: supplying, by at least one hydraulic cylinder-type steam compressor, the superheated steam to the hydraulic cylinder-type pressurized reactor; recovering hydraulic pressure of a hydraulic pressure chamber of the hydraulic cylinder-type pressurized reactor into a hydraulic pressure chamber of the hydraulic cylinder-type steam compressor at a time of reducing pressure in the hydraulic cylinder-type pressurized reactor to a pressure of the supercritical or subcritical state or lower after the cellulosic biomass has been hydrolytically saccharified, wherein a hydraulic pressure return passage of the hydraulic cylinder-type pressurized reactor and the hydraulic pressure chamber of the hydraulic cylinder-type steam compressor are in a state of connection via a hydraulic pressure recovery passage; and after supplying the slurry, the cellulosic biomass of which has been hydrolytically saccharified, into a flash tank, flash-evaporating the slurry and recovering flash steam into the hydraulic cylinder-type steam compressor.
 2. The method of hydrolytic saccharification of cellulosic biomass according to claim 1, wherein the at least one hydraulic cylinder-type pressurized reactor comprises a plurality of hydraulic cylinder-type pressurized reactors, and the at least one hydraulic cylinder-type steam compressor comprises a plurality of hydraulic cylinder-type steam compressors, and the number of hydraulic cylinder-type steam compressors, which perform the supplying of the superheated steam to the hydraulic cylinder-type pressurized reactors, is the same as the number of hydraulic cylinder-type pressurized reactors, the method comprising cyclically recovering the hydraulic pressure of the hydraulic pressure chamber of each hydraulic cylinder-type pressurized reactor into the hydraulic pressure chamber of a corresponding one of the hydraulic cylinder-type steam compressors at the time of reducing the pressure in the hydraulic cylinder-type pressurized reactor to the pressure of the supercritical or subcritical state or lower after the cellulosic biomass has been hydrolytically saccharified, wherein the hydraulic pressure return passage of each hydraulic cylinder-type pressurized reactor and the hydraulic pressure chamber of the corresponding hydraulic cylinder-type steam compressor are in the state of connection via the hydraulic pressure recovery passage.
 3. The method of hydrolytic saccharification of cellulosic biomass according to claim 1, wherein the hydraulic pressure recovery passage is formed as a single passage at a portion connecting to the hydraulic pressure return passage and at a portion connecting to the hydraulic pressure chamber of the hydraulic cylinder-type steam compressor, and a remaining portion of the hydraulic pressure recovery passage is divided into a plurality of sub-passages, and each sub-passage is provided with a corresponding one of air chambers which are assigned different pressure storage setting values, respectively, the method comprising: storing the hydraulic pressure of the hydraulic pressure chamber of the hydraulic cylinder-type pressurized reactor sequentially in the air chambers in descending order of the pressure storage setting value; and then releasing the hydraulic pressure sequentially from the air chambers in ascending order of the pressure storage setting value to supply the hydraulic pressure to the hydraulic pressure chamber of the hydraulic cylinder-type steam compressor.
 4. The method of hydrolytic saccharification of cellulosic biomass according to claim 1, wherein a steam generator is connected to the flash tank, the method comprising: mixing steam supplied from the steam generator and the flash steam; and supplying resultant steam to the hydraulic cylinder-type steam compressor.
 5. The method of hydrolytic saccharification of cellulosic biomass according to claim 1, wherein an air and/or nitrogen supply device is connected to at least one of the flash tank and steam piping connecting the flash tank and the hydraulic cylinder-type steam compressor, the method comprising mixing air and/or nitrogen into steam to be supplied to a steam compression chamber of the hydraulic cylinder-type steam compressor, such that the air and/or nitrogen mixed into the steam is in an amount that is not less than 1/7 and not more than ⅓ of an amount of the steam.
 6. An apparatus for hydrolytic saccharification of cellulosic biomass comprising: at least one hydraulic cylinder-type pressurized reactor configured to pressurize slurry of cellulosic biomass together with superheated steam into a supercritical or subcritical state; at least one hydraulic cylinder-type steam compressor configured to supply the superheated steam to the hydraulic cylinder-type pressurized reactor; and a flash tank configured to be supplied with the slurry that is removed from the hydraulic cylinder-type pressurized reactor, the slurry being in a high-temperature and high-pressure state, and to flash-evaporate the slurry, wherein a hydraulic pressure return passage of the hydraulic cylinder-type pressurized reactor and a hydraulic pressure chamber of the hydraulic cylinder-type steam compressor are connected via a hydraulic pressure recovery passage, hydraulic pressure of a hydraulic pressure chamber of the hydraulic cylinder-type pressurized reactor is recovered into the hydraulic pressure chamber of the hydraulic cylinder-type steam compressor through the hydraulic pressure recovery passage, the flash tank is connected to the hydraulic cylinder-type steam compressor, and flash steam generated from the slurry in the high-temperature and high-pressure state is recovered into the hydraulic cylinder-type steam compressor.
 7. The apparatus for hydrolytic saccharification of cellulosic biomass according to claim 6, wherein the at least one hydraulic cylinder-type pressurized reactor comprises a plurality of hydraulic cylinder-type pressurized reactors, and the at least one hydraulic cylinder-type steam compressor comprises a plurality of hydraulic cylinder-type steam compressors, the number of hydraulic cylinder-type steam compressors, which supply the superheated steam to the hydraulic cylinder-type pressurized reactors, is the same as the number of hydraulic cylinder-type pressurized reactors, the hydraulic pressure return passage of each hydraulic cylinder-type pressurized reactor is connected to the hydraulic pressure chamber of a corresponding one of the hydraulic cylinder-type steam compressors via the hydraulic pressure recovery passage, the hydraulic pressure of the hydraulic pressure chamber of each hydraulic cylinder-type pressurized reactor is recovered into the hydraulic pressure chamber of the corresponding hydraulic cylinder-type steam compressor via the hydraulic pressure recovery passage, the flash tank is connected to the plurality of hydraulic cylinder-type steam compressors, and the flash steam generated from the slurry in the high-temperature and high-pressure state is cyclically recovered into the plurality of hydraulic cylinder-type steam compressors.
 8. The apparatus for hydrolytic saccharification of cellulosic biomass according to claim 6, wherein the hydraulic pressure recovery passage is formed as a single passage at a portion connecting to the hydraulic pressure return passage and at a portion connecting to the hydraulic pressure chamber of the hydraulic cylinder-type steam compressor, and a remaining portion of the hydraulic pressure recovery passage is divided into a plurality of sub-passages, each sub-passage is provided with a corresponding one of air chambers which are assigned different pressure storage setting values, respectively, and the hydraulic pressure of the hydraulic pressure chamber of the hydraulic cylinder-type pressurized reactor is sequentially stored in the air chambers in descending order of the pressure storage setting value, and then the hydraulic pressure is released sequentially from the air chambers in ascending order of the pressure storage setting value and supplied to the hydraulic pressure chamber of the hydraulic cylinder-type steam compressor.
 9. The apparatus for hydrolytic saccharification of cellulosic biomass according to claim 6, wherein a steam generator is connected to the flash tank, and steam supplied from the steam generator and the flash steam are mixed, and then resultant steam is supplied to the hydraulic cylinder-type steam compressor.
 10. The apparatus for hydrolytic saccharification of cellulosic biomass according to claim 6, wherein an air and/or nitrogen supply device is connected to at least one of the flash tank and steam piping connecting the flash tank and the hydraulic cylinder-type steam compressor, and air and/or nitrogen is mixed into steam to be supplied to a steam compression chamber of the hydraulic cylinder-type steam compressor, such that the air and/or nitrogen mixed into the steam is in an amount that is not less than 1/7 and not more than ⅓ of an amount of the steam. 